1. Field of the Invention
The present invention relates to a tension control apparatus using a dancer roller device which applies tension to a linear body such as an optical fiber and a wire.
2. Related Background Art
Conventionally known as a tension control apparatus for a linear body is the one disclosed in Japanese Patent Application Laid-Open No. 6-255885. As shown in FIG. 12, this apparatus comprises guide rollers 2 and dancer rollers 3, about both of which a running linear body 10 is wound. The dancer rollers 3 are installed so as to be movable relative the stationary guide rollers 2 approximately in the vertical directions (along a line connecting the respective rotational center axes of the guide rollers 2 and dancer rollers 3), and apply the predetermined amount of the tension to the linear body 10 by holding the dancer rollers 3 at a predetermined position (control midpoint position). For this tension adjustment, the tension control apparatus comprises a torque motor 102 for variably controlling the tension applied to the linear body 10, an arm 4 for applying a moment produced by a torque of the torque motor 102 to dancer rollers 3, a tension detector 91 for detecting the tension of the linear body 10, and a tension control means 100 for receiving an output signal of the tension detector 91 and supplying a drive signal to the torque motor 102.